This invention relates generally to fuel preheating means for use on heat engines, and more particularly to such means for preheating the gasoline fuel of an automobile or the like, prior to its introduction to the carburetor of the vehicle, through utilization of waste heat from the vehicle's exhaust or, in some cases, from its coolant.
It is well known that gasoline fuel burns most efficiently in an internal combustion engine when it is in the form of a vapor. The conventional carburetor does not convert all of the gasoline passing therethrough into vapor, a substantial portion being, instead, merely broken up into tiny droplets that remain suspended in the intake air when the resulting mixture of fuel and air is drawn through the mainfold and into the cylinders of an engine. While some vaporization takes place, a substantial portion of the gas remains in the form of liquid droplets in the cylinder head at the time the mixture is ignited by the spark. These liquid fuel droplets burn inefficiently, or incompletely, with the result that the engine exhaust contains an excessive amount of unburned hydrocarbons and carbon monoxide as air pollutants which contribute to the formation of atmospheric smog. Nitrogen oxide is also formed, as a smog producing pollutant in the exhaust, because of high combustion temperature in the engine, particularly at the point where the exhaust gases pass through the exhaust ports during the first few degrees of valve opening. These high temperatures are brought about when minute droplets of liquid fuel, still unburned, are vaporized by the heat of combustion to mix with the remaining oxygen, so that afterwards there is delayed combustion at an exceedingly high temperature when the gas is passed between the face of the valve and the valve seat. This high temperature is responsible for formation of the nitrogen oxide found in internal combustion engine exhaust gases.
In addition to the above-noted disadvantages of the incomplete combustion of gasoline brought about by incomplete vaporization thereof in carburetors, there is a further disadvantage in the fact that such incomplete combustion results in deposits of carbon on interior engine surfaces. Furthermore, incomplete fuel combustion is wasteful of energy, a serious enough problem in the past but one which is now approaching catostrophic proportions because of oil shortages in this country and the rising price of imported oil from the oil producing nations.
Various means for preheating the fuel to automobile engines have been proposed in an effort to increase engine efficiency and cut down on exhaust pollutants. All such fuel preheating means of which I am aware have been designed to provide heat to the fuel as it passes between the carburetor and intake manifold of the engine. U.S. Pat. No. 3,762,385 to Hollnagel discloses a device adapted to heat engine fuel in this manner. While such devices are claimed to increase automobile gas mileages and reduce exhaust pollutants, none has yet, to my knowledge, met with any substantial degree of commercial acceptance. In view of the critical need today for more efficient fuel burning engines, the absence of such acceptance of any fuel preheating means heretofore known is clear evidence that no such means capable of meeting the stringent demands of the marketplace has yet been provided. Moreover, those prior art devices adapted to heat gasoline fuel from an engine carburetor prior to its introduction into the intake manifold do nothing to reduce or eliminate any exhaust pollutants resulting from the presence of additives in commercial gasoline fuels. The most common pollutant of this type, to my knowledge, is lead, which is spewed out from millions of automobile exhaust pipes to poison the atmosphere in the vicinity of heavily traveled roadways.